284 EMBRYOLOGICAL METHODS. 



method of shelling, but prefers fixing in acetic-acid sublimate, or 

 liquid of Perenyi. 



HEYDER (Zeit. wiss. ZooL, xciii, 1909, p. 92), before imbedding 

 embryos of Arion that have been fixed with sublimate, treats them 

 for an hour or two with carbonate of soda of -^ to T X F per cent., 

 which makes the stomach and intestine less brittle. 



GATENBY (Quart. Journ. Micr. Science, 1919), for Limncea stagnalis 

 ova, used Flemming's strong fluid without acetic acid, Champy's 

 fluid for two days to a week, and Kopsch's method. 



HOLMES (Journ. of Morph., 1900, p. 371) teases the egg-capsules of 

 Planorbis in nitrate of silver of f per cent., exposes to sunlight until the 

 cell-limits come out, rinses with 0-2 per cent, hyposulphite of soda, puts 

 for a few minutes into picric acid, and then through alcohol into balsam. 



See also WASHBUBN, Amer. Anat., xxviii, 1894, p. 528 (liquid of Flem- 

 ming, or 0-3 per cent, chromic acid, or 1 per cent, osmic acid, followed 

 by liquid of Merkel). 



CONKLIN (Journ. of Morph., xiii, 1897, p. 7) fixes ova of Crepidula for 

 fifteen to thirty minutes in picro -sulphuric acid, and stains with dilute 

 acidified hcematoxylin of Delafield. 



KOSTANECKI and WIERZEJSKI (Arch. mik. Anat., xlvii, 1896, 

 p. 313) fix the spawn of Physa, fontinalis either in 1J to 2 per cent, 

 nitric acid, or in " sublimate and 3 per cent, nitric acid in the pro- 

 portion of 2 : 1," and bring through successive alcohols. They 

 imbed entire ova in paraffin, but isolated embryos in celloidin. 



621. CHITON, see METCALF, Stud. Biol. Lab. Johns Hopkins Univ., v, 

 1893, p. 251. (Ova with young embryos put for twenty to forty-fiv r e 

 seconds into eau de Labarraque, then into water, in which the chorion 

 swells and can easily be removed.) 



622. Lamellibranchiata. STAUFFACHER (Jena Zeit., xxviii, 1893, 

 p. 196) fixes embryos of Cyclas in sublimate, stains with hsemalum, 

 and cuts in paraffin. 



LILLIE (Journ. of Morph., x, 1895, p. 7) fixes ova of Unio for 

 ten to twenty minutes in liquid of Perenyi, and preserves them in 

 70 per cent, alcohol, or advanced embryos with liquid of Merkel or 

 sublimate, larvae with 0-05 to 0-1 per cent, osmic acid, preserving 

 them in glycerin. Grlochidia may be cut with the shell in paraffin 

 of 58 melting-point ; they may be anaesthetised with chloral hydrate 

 before fixing. 



Arthropoda. 



628. Fixation of Ova. In many cases the ova of Arthropods are 

 best fixed by heat ( 13). This may be followed either by alcohol 

 or some watery hardening agent. If it be desired to avoid heating, 

 picro-nitric acid may be tried. 



